Enzyme Catalysis Lab

Purpose

The purpose of this experiment is to observe the change of hydrogen peroxide to water and oxygen gas by an enzyme catalase as well as to measure how much oxygen was made and calculate the rate of the enzyme-catalyzed reaction.

Introduction

Enzymes are proteins made from living cells that acts as a catalyst which affects the rate of a chemical reaction. In an enzyme-catalyzed reaction, the substrate binds  the active site of the enzyme. Each enzyme is specific for a certain reaction because each into acid sequence is unique and enzyme can be affected by the salt concentration, pH, temperature and activations and inhibitors.

Methods

We first created a base line in order to determine the hydrogen peroxide that is initially in the solution and use that base line to see the uncatalzyed rate of decomposition versus the catalyzed rate of decomposition. Sulfuric acid is added to inhibit the enzymes because of the acidic environment and cause it to stop reacting. After adding sulfuric acid, a 5-mL sample is taken in order to be titrated to see the catalyzed rate or change over time. potassium permanganate is added drop by drop from a burette until the solution is turned a pink or brown color.

Cups to be mixed fit various amounts of time.

When testing the baseline sample, there is initially a brown/pink color, but with some stirring, that hue disappears (pictures 1 & 2).  Once some potassium permanganate is in the solution and the color doesn't dissolve, the reaction has reached the end (picture 3).

Adding catalase extract (yeast) to begin reaction.

Adding Sulfuric Acid to stop reaction.

Taking a 5mL sample to test with potassium permanganate.

Test with potassium permanganate until there is a consistent pink or brown color.


Data

Discussion

The overall objective of the experiment was to observe the relationship between Hydrogen Peroxide and the catalase extract.  More specifically, observing the transformation of Hydrogen Peroxide to water and oxygen gas due to an enzyme catalase (in this case, the enzyme catalase was yeast).  Each time another aspect of the experiment was conducted, aka the catalase was left in the Hydrogen Peroxide for a longer period of time, the results varied.  From ten seconds to thirty seconds to sixty seconds, the amount of Potassium Permanganate consumed was sporadic, going from 3.2mL to 2.8mL, then back up to 3mL.  While these results were all very close, no true patterns were apparent.  In general, the amount of Potassium Permanganate consumed decreased between ten seconds and 360 seconds of the Hydrogen Peroxide solutions being mixed with the yeast.  The same applies to the amount of Hydrogen Peroxide used throughout the reaction: there was a general trend of decreasing of the usage of the solution as the length of time increased--although there were multiple instances in which the data did not follow the trend exactly.  For example, from ten seconds to thirty seconds to sixty seconds, the amount of Hydrogen Peroxide used initially decreased, but then increased right after.  The interval of time from 0-10 seconds had the highest rate because that is when there were the most enzymes and substrates present.  It is clear that the interval of 180-360 seconds had the lowest rate, which is because by the time the solution had been being mixed for so long, most of the enzymes and substrates were essentially used up, causing the reaction to plateau.  Since there was a relatively sure and consistent amount of the Hydrogen Peroxide, enzyme catalase, and Sulfuric Acid being used in each sample, and each time a titration took place, it was always with 5mL of the entire solution, the inconsistencies most likely come from the titration part of the experiment.  It is very easy to let a little too much Potassium Permanganate through the titration at once.  If too much is released when the pink or brown color was already sticking around, the results could easily be impacted.  To improve this experiment in the future, it would be important to make sure all measurements are accurate--from the amount of each solution used, to the amount of time each solution is mixed for.

Conclusion

Through this lab we observe how the catalase increases rate of decomposing of hydrogen peroxide. We see how hydrogen peroxide and enzyme catalase are able to work together. With the different time trials we are able to see how the enzyme breaks down hydrogen peroxide over a period of time. Uncatalzyed decomposition is slower than catalyzed decomposition of hydrogen peroxide. The catabolic process helps to speed up decomposition and break down, an example of our liver's ability to break down toxins.